A whole group of writers seem to misunderstand the significant difference between these two similar-sounding words.

A core is the central or most important part of something: The puppet government was corrupt to its core.

A corps, however, is a division of military personnel, usually those who have a specialized function: The Marine Corps landed on the beaches shortly before dawn.

A good way to remember this is that corps, because of its s, look like it’s plural, hence a group, while core has no s and so looks like it’s singular, hence a lone, single axis at the center of a larger thing.

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My name is Rob Bignell. I’m an affordable, professional editor who runs Inventing Reality Editing Service, which meets the manuscript needs of writers both new and published. I also offer a variety of self-publishing services. During the past decade, I’ve helped more than 300 novelists and nonfiction authors obtain their publishing dreams at reasonable prices. I’m also the author of the 7 Minutes a Day… writing guidebooks, four nonfiction hiking guidebook series, and the literary novel Windmill. Several of my short stories in the literary and science fiction genres also have been published.